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5 points by eds 6131 days ago | link | parent

Actually, if you are using Anarki, a lot of the slowness comes from infix.arc redefining math operators. Just removing infix.arc from libs.arc will increase the speed of math operations by about an order of magnitude. In fact, removing infix.arc actually produced more of a speedup for me than using your ffi.

With infix.arc:

  arc> (def fib (n)  (if (< n 2) 1 (+ (fib (- n 1)) (fib (- n 2)))))
  #<procedure: fib>
  arc> (time (fib 30))
  time: 34672 msec.
  1346269
Without infix.arc:

  arc> (def fib (n)  (if (< n 2) 1 (+ (fib (- n 1)) (fib (- n 2)))))
  #<procedure: fib>
  arc> (time (fib 30))
  time: 4219 msec.
  1346269
With ffi:

  arc> (w/ffi "gs1771.so"
  (cdef _< "inf" cbyte (clong clong))
  (cdef - "minus" clong (clong clong))
  (cdef + "plus" clong (clong clong)))
  #<primitive:ffi:plus>
  arc> (def < (a b) (is 1 (_< a b)))
  #<procedure: <>
  arc> (def fib (n)  (if (< n 2) 1 (+ (fib (- n 1)) (fib (- n 2)))))
  #<procedure: fib>
  arc> (time (fib 30))
  time: 6907 msec.
  1346269


3 points by almkglor 6131 days ago | link

Dang.

Personally I don't even use infix. If the slowdown comes from that...

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2 points by eds 6131 days ago | link

Yeah, sorry about that. I wasn't thinking about performance when I originally put infix.arc up on Anarki, and since I was doing a lot of testing at the time I found it convenient to add it to libs.arc. Perhaps it would be best to leave it out by default though.

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2 points by eds 6131 days ago | link

Done. You shouldn't get any more performance hits from infix math unless you explicitly load infix.arc.

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1 point by sacado 6131 days ago | link

Oh that's right... On my machine, the FFI version is still a little faster (about 20% faster), but not that much. It now deals more efficiently with boolean values however, that might explain it... Anyway, I don't know if it's worth using FFI this way now... Not until we can compile Arc code to efficient C code at least :)

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